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No 881,636. PATENTED MAR. 10, 190 8. 'D. P. THOMSON..

GAB SIGNAL SYSTEM.

APPLICATION FILED AUG. 2, 1907.

DAvn: PTHnmsuN.

DAVID B. THOMSOKOF SCHENEOTADY, NEW YORK, ASSIGNOR TO To all whom timer concern:

ar-citizenof the United States, residingat I commonly employed in signal systems, and

"ofNew York,

- UNITED STATES PATENT onnron GENERAL EL ornic con- PnNY, A CORPORATION on NEW YORK. a

CAB SIGNAL SYSTEM.

No. 881,635. Specification of Letters Patent. Patented March 10, 1908;

Application filed August 2, 1907. Serial No. 386749.

Iwhile transformers C and '0}? have their secondaries similarly connected,. but their primaries supplied from generator B The transformers supplied froin-the two generators alternate so that adjacent transformers supply currents of different fre uencies Be, it known that I, DAVID P. THoMsoN,

Schenectady, county of Schenectady, State. l have invented certain new and I useful Improvements in Cab *Signal Systerns, of which the following is a specificato the track. D represents a car or ocomo- .tlon, tive moving in the direction of the arrow and "My invention relates to cab signal systems, and is particularly applicablev to electric readsv operated by direct. current, since it doesnotarequire the insulating rail joints carrying coils E E infront of the front wheels.- These coils may conveniently; be mounted as shown in Fig. 2, between-the pilot and front wheels of the locomotive.

n this position the coil is .protectedqfrom therefore the railsma'y be used'as return conmechanical injury by. the pilot. The coil is ductor for the power-current, and also since preferably wound on a magnetic corezla niit is not affected b the presence of direct nated in planes transversetotheraildength. current in the tracl; A telephone receiver F or'other indicating My invention consists in making both' device is connected to thecoils E E. r track rails conductir'ely continuous and con- .With a locomotive in the position. shown carried in front of the front wheels and in inductive relation to the .the sources ahead of the locomotive back is enabled to tell current-only from the u my invention; and Figs.

i. p, generators of different frequencies.

as a telephone receiver,

is indicated by necting sources of alternating-current at inin Fig. 1, if no other car ortrain is'between tei'vals'across the track-rails, and providing l the locomotive and the transformer Cfi-curthe-locomotiveor other vehicle with a coil rent flows from this transformer throughthe rails and through the locomotive aXles,;an'd acting inductively in the telephone receiver F a cu'rrent'corre .sponding in frequency to that of thegenerator B. If no train is between the transformers C and C former C through the rails and locomotive axles, thereby inducing a second current in the coils E E of a frequency corresponding to generator B. Thus, if a train is between the locomotive and the first transformer ahead, the coils E E receive no current at all. :If no train is between the locomotive and the .first' transformer, but if there is-a train between thefirstand second transformers ahead of the locomotive, then current of a single frequency, while if no train is between the locomotive and the second transformer ahead, then the coils E E receive currents of two frequencies. In this Way three different indications'may absence of noise in the receiver indicating danger, a note corresponding to 'onefrequ e'ncy representing caution, and a' note'correspondrails and with an f electro-responsive indicating device, such connected to the coil. The alternating-current flowing from through the rails and through the locomotive axles induces a current in the coil which the telephone receiver or other indicatin device. In such a system, dications ma be given, I make adjacent sources supp y currents 'of different frequencies, so that the motorman or engineer whet-her he is receiving source immediately ahead of him or from two sources, and consequently knows whether one or two blocks ahead are clear.

My invention will best be understood by reference to, the accompanying drawings, 1n hioh 1 ure 1 showsdia ammatically a cab sigmil system arranged in accordance 2 and 3 show a sultablev arrangement and construction of the coils on the locomotive. p

In the drawings'A represents the trackrails, B B represent two alternating-current Transormers C, C and C have their primaries supplied from the generator B and their secondaries connected across the track,

representing clear. I the two frequencies, the caution'andclea'r indications may' readily be distinguisheiisinde with both frequencies flowing-throughthe track a note is obtained corresponding-tothe difference in the two frequencies. F or instance, if the generators B and B current of 250 and 300 cycles, respectively,

on the coils E E produces supply current also flows from transthe coils E receive be given;

ing to the two frequencies simultaneously By: properly selecting i sources ahead of the locomotive,

then a caut on signal. wul'be represented by relation to the alternating-current in the a note corresponding to either 250 or 300 cyrails, and elcctro-responsive means on the cles, While clear will be represented by a note vehicle connected 'to the corresponding to 50 cycles. Other frequencies, may, of course, be employed than those mentioned. close to one transformer there is a tendency for the current supplied by that transformer with a railway havin to increase so that that frequency tends to predominate so great y as to drown out the effect of the other frequency. This effect, however may be overcome sufficiently for ractical purposes by means of resistances G inserted in the secondary circuits of the sup- 1y transformers. By properly proportionmg these resistances the current when a train is almost directly over the secondary terminals of the transformer may be prevented from increasing too greatly. These resistances further serve to prevent saturation of the transformer core by the power current when the system is applied to an electrically Operated road.

While I have illustrated and prefer to use a telephone receiver in combination with dif-' ferent frequencies on the track,.since this affords simple and effective means for distinguishing the currents from two different it will be understood that my invention in its broader aspect is not limited to this specific combination, but that other indicating means may be employed with other arrangements for supplying inductively to the indicating means from two points ahead of the train currents which may be distinguished by the indicating means.

' What I claim as new and desire to secure by Letters Patent of the United States, is,

1. In a cab signal system, in combination with a railway having both rails conductively continuous and having sources of alternating-current connected at intervals across the rails, a coil carried by a vehicle in front of the front wheels and in inductive relation to the alternating-current in the rails, and electro-responsive means on the vehicle connected to said coil.

2. In a cab signal system, in combination with a railway having bothrails conductively continuous and having sources of alternating-current connected at intervals across the rails, a coil carried by a vehicle in front of the front wheels and in inductive relation to the alternating-current in the rails, and electro-responsive means on the vehicle energized by the current induced in said coil and adapted to produce a signal indication.

3'. In a cab signal system, in combination with arailway having both rails conductively continuous and having sources of alternating current connected at intervals across the rails, a coil carried by a vehicle in front of the-front wheels and in inductive Of course when the train is i ahead of the vehicle.

.affect said indicating meansby inductive prislng a coil carried in front of the front affect said indicating means coil and adapted to indicate the inductive action on said coil of current from a plurality of said sources 7 4. In a cab signal system, in combination.

g both rails conductively continuous and having sources of alternating-current connected at intervals across the rails, adjacent sources being of differentcharacter, a coil carried by a vehicle in front of the front wheels and in inductive relation to the current in the rails, and electro-responsive means connected to said coil and adapted to indicate the presence in said coil of a plurality of currents of different character.

5. In a cab signal system, in combination with a railway having both rails conductively continuous and having sources of alternating-current connected at intervals across the'rails, adjacent sources being of different frequency, a coil carried by a vehicle in front of the front wheels and in inductive relation to the current in the rails, and electro-responsive means connected to the coil and adapted-to give different indications for the resence in sai coil of two frequencies simu taneously and of one frequency only. i

6. In combination with a railway having both rails conductively continuous, cab signal apparatus carried by a vehicle, comprising a coil carried in front of the front wheels and in inductive relation to the rails and electro-responsive indicating means connected to the coil, and means for supplying to the rails at intervals currents adapted to action on said'coil. I 7. In combination with a railway having both rails condu'ctively continuous, cab signal apparatus carried by a vehicle, comwheels and in inductivelrelation to the rails and electro responsive indicating means'connected to the coil,.and means for-supplying to the rails at intervals'currents adapted to by inductive action on said coil, the currents supplied from adjacent sources being adapted to pro: duce distinguishable effects on said indicat ing means.

8 Ina cab signal system, in combination with a railway having both rails conductively continuous and having sources of alternating-current connected at intervals across the-rails, adjacent sources being of different frequency, a coil/carried by .a vehicle in front of the front wheels and in inductive relation to the current in the rails,

and a telephone receiver connected to the coil.

9. In a cab'signal system, in combination with a railwa ively continu alternating-current connected at intervals across the mills, a m

the vehicle in adjacent to one of laminated in length, a coil wound responsive indicating connected to said coil.

10. In a cab signal system, in combination With. a railway i-vely continu y having both rails conductalternatin ous and having sources of across the vehicle in a netic core carried by front oi the front wheels and the rails, said core being planes transverse to the railon said core, and electroineans on the vehicle having both rails conductous and having sources of g-current connected at intervals rails, a magnetic core carried by a front of the front wheels and adplanes Wound facent to oneof the rails, said core being aminated in length, a coil phone receiver conne In witness whereo hand this first day of A transverse to the railon said core, and a telected to said coil.

, I have hereunto set my DAVID THOMSON.-

Witnesses:

BENJAMIN B. HULL, HELEN ORFORD. 

